Coleoid cephalopods through time (Warnke K., Keupp H., Boletzky S. v., eds) Berliner Paläobiol. Abh. 03 141-162 Berlin 2003 MUSCLE ARRANGEMENT, FUNCTION AND SPECIALIZATION IN RECENT COLEOIDS W. M. Kier* & J. T. Thompson Department of Biology, CB# 3280 Coker Hall, University of North Carolina, Chapel Hill, NC 27599-3280, USA *corresponding author:
[email protected] ABSTRACT The bodies of coleoid cephalopods are characterized by a dense musculature consisting of tightly packed bundles of muscle fibers arranged in three mutually perpendicular planes. This arrangement of muscle, termed a ‘muscular hydrostat’, generates force and also provides skeletal support. Muscle function during movement and locomotion thus does not depend on rigid skeletal elements, even though many extant coleoids possess hard parts. In this review, we describe the arrangement and microanatomy of the musculature and connective tissues from a variety of coleoids and from a range of cephalopod organs and systems including the mantle, funnel, fins, arms, tentacles, and suckers. We analyze the muscle and connective tissues from the standpoint of biomechanics in order to describe their function in movement and locomotion. This analysis demonstrates that the same basic principles of support and movement are shared by all of these structures. In addition, the crucial role played by fibrous collagenous connective tissues in these systems is emphasized. Further work is required, however, to describe the mechanical functions of the musculature of the diverse pelagic cephalopods, to understand neuromuscular control of these complex systems, and to explore the mechanisms of specialization of coleoid cephalopod muscle. INTRODUCTION dense musculature consisting of tightly packed bundles of muscle fibers arranged in three mutually Although many recent coleoids retain hard parts, they perpendicular directions (see Budelmann et al.